The present invention relates to semiconductor manufacturing, and more particularly, to a method for forming metal line of highly integrated semiconductor devices.
As a density of an integrated semiconductor device increases, a width of a pattern and a space between patterns become smaller. Since it needs to use a shorter wavelength for forming patterns having a narrow space in lightening process, the wavelength of a stepper is getting shorter and a deep ultraviolet wavelength (DUV) light become to be used.
According to using a shorter light such as DUV, a TiN anti-reflective coating layer which is over a metal line, doesn't effectively prevent the metal line from reflecting. Thus, since diffused reflection may be occurred during lightening, it is difficult that a resulting metal line pattern is not finely and accurately formed. To solve the diffused reflection, a oxynitride has been formed on the TiN layer, or an anti-reflective coating layer has been made from aluminum nitride. However, in the former method, the number of process steps is increased and it is not easy to make via contact hole for connecting an interlayer metal, and the resistance height of a metal line is increased. Also, the latter method has a problem that the anti-reflective coating layer must be removed in a following process and the metal line with aluminum nitride on top has electromigration resistance.